Helen and Sergey must cut down a row of trees. Helen can cut down the entire row in 3 hours, and Sergey can cut down the

Expert replies

Previous Topic Next Topic

Gmat_mission: Legendary Member; Posts: 1622; Joined: Thu Mar 01, 2018 7:22 amFollowed by: 2 members

by Gmat_mission » Sun Jun 14, 2020 1:55 pm

Timer

00:00

Your answer

Difficulty–

right wrong

Pick an answer to see how members did

Helen and Sergey must cut down a row of trees. Helen can cut down the entire row in 3 hours, and Sergey can cut down the entire row in 7 hours. If they simultaneously start cutting trees, each starting at one end of the row and working towards each other, what fraction of the trees will Sergey have cut at the time they meet?

A. 1/10
B. 3/10
C. 3/7
D. 4/7
E. 7/10

[spoiler]OA=B[/spoiler]

Source: Princeton Review

Source: Beat The GMAT — Problem Solving | Sun Jun 14, 2020 1:55 pm

GMAT/MBA Expert

Scott@TargetTestPrep: GMAT Instructor; Posts: 8246; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

Re: Helen and Sergey must cut down a row of trees. Helen can cut down the entire row in 3 hours, and Sergey can cut down

by Scott@TargetTestPrep » Tue Jun 23, 2020 8:26 am

Gmat_mission wrote: ↑
Sun Jun 14, 2020 1:55 pm
Helen and Sergey must cut down a row of trees. Helen can cut down the entire row in 3 hours, and Sergey can cut down the entire row in 7 hours. If they simultaneously start cutting trees, each starting at one end of the row and working towards each other, what fraction of the trees will Sergey have cut at the time they meet?

A. 1/10
B. 3/10
C. 3/7
D. 4/7
E. 7/10

[spoiler]OA=B[/spoiler]

Solution:

We can assume there are 21 trees. So Helen’s rate is 21/3 = 7 trees per hour and Sergey’s rate is 21/7 = 3 trees per hour. We can create the equation where x is the number of hours it takes to cut down all 21 trees when they work together:

7x + 3x = 21

10x = 21

x = 2.1

In 2.1 hours Sergey cuts 3 * 2.1 = 6.3 trees, which is 6.3/21 = 63/210 = 3/10 of the trees.

Answer: B

Scott Woodbury-Stewart
Founder and CEO
[email protected]

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

Featured schoolRound 2 closes Jan 7, 2027 54 days left

Chicago Booth

Since 1982, 10 Booth faculty members have received the Nobel Prize in Economic Sciences, more than any other business school.

#3
U.S. News rank: $175,000
Median base salary: 670
Average GMAT Focus: 635
Students in the class

Apply to Booth Visit chicagobooth.edu See the full profile

Photo: Warren LeMay, CC BY-SA 2.0

GMAT Course Reviews

563 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (563 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review